The present invention relates to a method for preparing polyisoolefins having exclusive xe2x80x98exoxe2x80x99 terminal double bond chain ends, the polyisoolefins having exclusive xe2x80x98exoxe2x80x99 terminal double bonds, a method for preparing a star-branched polymeric material from the polyisoolefin and a dendrimer, and the functionalized polyisobutylenes and the star-branched polymeric materials prepared by these methods. The present invention also relates to blends of polyolefins and the star-branched polymer, and films and fibers made from these blends. The present invention also relates to a method for preparing star-branched polymeric material from a polyolefin and a hydrolytically stable dendrimer and the star branched material prepared by this method.
Dendrimers are well defined globular molecules. These are generally prepared by stepwise or reiterative reaction of multifunctional monomers to obtain a branched structure. In U.S. Pat. No. 5,530,092, for example, the repetition of double Michael addition of acrylonitrile starting with a primary diamine followed by hydrogenation obtains two primary amines for each initial amine. This doubles the number of primary amine groups. Thus, beginning with a diamine, the first generation dendrimer (G1) has four primary amines; the second generation (G2) has eight primary amines; the third generation (G3) has sixteen primary amines; the fourth generation (G4) has thirty-two primary amines; the fifth generation (G5) has sixty-four primary amines in the outer shell, and so on. These polyamine dendrimers are said to be stable to degradation through hydrolysis reactions.
Amine-terminated polyamidoamine, polyethyleneimine and polypropyleneimine dendrimers are also known, for example, from U.S. Pat. Nos. 5,393,797; 5,393,795; 5,560,929; and 5,387,617, all to Hedstrand et al.
Polyisobutenyl succinimide-polyamidoamine dendrimer star-branched polymers obtained by reacting second generation polyamidoamine dendrimers with polyisobutenyl succinic anhydride are disclosed in Migdal""s U.S. Pat. No. 4,938,885 [to Migdal]. These polymers are said to have dispersancy powers in lubricating oils and to exhibit antioxidant activity. However, these products are not hydrolytically stable.
U.S. Pat. No. 4,316,973 discloses telechelic olefin polymers such as telechelic diolefin polyisobutylene prepared by refluxing dihalogen polyisobutylene in tetrahydrofuran with a strong base such as potassium t-butoxide. This is said to produce a product which has 1H NMR spectroscopy at 60 MHz consistent with a terminal vinylene functionality of 2.0.
Boerzel et al., U.S. Pat. No. 4,152,499, discloses polyisobutylene said to contain a proportion of double bonds reactive with maleic anhydride of from 60 to 90 percent of the double bonds present in the polyisobutylene. The polyisobutylenes are prepared using a boron trifluoride polymerization initiator with a short polymerization time.
Bronstert et al., U.S. Pat. No. 4,599,433, discloses the preparation of polyisobutylene-succinic anhydrides with titanium, zirconium or vanadium alkoxides as catalysts which are said to isomerize polyisobutylene during the reaction making it more reactive with the maleic anhydride. The polyisobutylene-succinic anhydride adduct is in turn reacted with a polyamine to obtain a lubricating oil additive.
The present invention arises, in part, from a method for preparing polyisobutylene having reactive terminal vinylidene groups. The process involves dehydrohalogenating halogen-terminated polyisobutylene in a hydrocarbon solvent using a metal alkoxide soluble in the hydrocarbon solvent this method does not require tetrahydrofuran (THF) as a solvent. This obtains a polyisobutylene terminated with an unsaturated end group which is in the reactive xe2x80x98exoxe2x80x99 form, and free of the corresponding xe2x80x98endoxe2x80x99 form. This method avoids the use of the undesirable tetrahydrofuran as a solvent. The presence of tetrahydrofuran renders the dehydrohalogenation reaction insufficiently stereospecific and introduces the possibility of peroxide formation.
In one aspect, the present invention comprises a method for preparing a polyisoolefin having double bond chain ends exclusively in the xe2x80x98exoxe2x80x99 form. The method includes the step of dehydrohalogenating the halogen-terminated polyisoolefin in a hydrocarbon solvent in the presence of hydrocarbon-soluble alkoxide. The halogen-terminated polyisoolefin is generally obtained by carbocationically polymerizing the isoolefin in the presence of a halogenating initiator according to techniques well known in the art to obtain halogen-terminated polyisoolefin. The preferred alkoxides are represented by the formula RO-M wherein R is alkyl of at least 5 carbon atoms and M is alkali metal. The polyisoolefin obtained from the carbocationic polymerization process can be telechelic, or in one embodiment is monohalogen-terminated. The isoolefin preferably has from 4 to about 12 carbon atoms, and more preferably is isobutylene. The alkoxide is preferably a branched alkoxide, more preferably tertiary-pentoxide (t-pentoxide), and the alkali metal can be one of lithium, sodium, cesium, rubidium, preferably potassium. The solvent should be essentially free of tetrahydrofuran. The method thus effected in accordance with the invention obtains polyisobutylene having a terminal double bond chain end in xe2x80x98exoxe2x80x99 form, essentially free of xe2x80x98endoxe2x80x99 form.
In another aspect, the invention comprises a method for preparing a star-branched polymeric material having a hydrophilic dendrimer core and hydrophobic polyolefin branches. The method includes reacting polyisoolefin-succinic anhydride with a dendrimer having primary amine functionality. The polyisoolefin-succinic anhydride is preferably polyisobutylene-succinic anhydride (PIBSA), most preferably prepared by the steps of: (1) carbocationically polymerizing isobutylene in the presence of a halogenating initiator, such as 2,4,4-trimethylpentyl chloride, to obtain monohalogen-terminated polyisobutylene; (2) dehydrohalogenating the monohalogen-terminated polyisobutylene in a hydrocarbon solvent in the presence of soluble alkoxide represented by the formula RO-M, R being an alkyl of at least 5 carbon atoms and M being an alkali metal; and (3) functionalizing the dehydrohalogenated polyisobutylene with maleic anhydride.
The star-branched polymer preparation preferably includes preparing the dendrimer by the steps of: (1) forming the double Michael addition product of acrylonitrile or methyacrylonitrile with a primary polyamine; (2) hydrogenating the double Michael addition product from step (1) to form primary polyamine functionality; and (3) optionally, repeating steps (1) and (2) using the product from step (2) to obtain higher generations of dendrimers.
The primary polyamine in the initial step (1) is preferably a diamine, such as, for example, 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane or the like.
The invention also includes terminally monomaleated polyisobutylene essentially free of unmaleated polyisobutylene, preferably less than 10 percent by weight of the polyisobutylene.
The invention also embraces the star-branched polymeric material prepared by the method described above which is essentially free of unreacted polyisobutylene. By using a mixture of two or more polyisobutylenes of different molecular weights the branches on each dendrimer core can have mixed lengths.
Moreover, the present invention includes star branched polymeric material comprising a hydrophilic dendrimer core with mixed branches of functionalized polyolefin and the polyisoolefin. The polyolefin branches can be a polymer or copolymer of ethylene, propylene, butylene or the like. Preferably, the polyisoolefin is polyisobutylene.
Moreover, the present invention includes star branched polymeric material comprising a hydrolytically stable dendrimer core with branches of polyolefins such as polyethylene, polypropylene, ethylene-propylene copolymers, and the like. The polyolefin is preferably polypropylene made with a metallocene catalyst.
The present invention also provides a composition comprising a blend of polyolefin, such as polyethylene, polypropylene, ethylene-propylene copolymers and the like, with a star-branched polymer comprising a dendrimer core and polyisoolefin branches or the mixed branches. The polyolefin is preferably polypropylene, more preferably polypropylene made with a metallocene catalyst. The blend has particular utility in films with improved tear and puncture resistance and controlled moisture/oxygen permeability.